Between a vehicle body and a wheel in a vehicle, a damper for generating a damping force and a suspension spring for biasing the damper in an expansion direction are provided in parallel. The suspension spring absorbs an impact caused by irregularity on a road surface, and the damper suppresses an expansion/contraction motion of the suspension spring associated with impact absorption. As a result, transmission of the impact caused by the irregularity on the road surface to the vehicle body is suppressed.
In a case where loads or occupants increase, compression amounts of the suspension spring and the damper become larger and a vehicle height becomes lower. In a case where loads or occupants decrease, the compression amounts of the suspension spring and the damper become smaller and the vehicle height becomes higher. Thus, it is known to mount a vehicle height adjusting apparatus capable of adjusting the vehicle height on a vehicle.
JP2010-149550A discloses a vehicle height adjusting apparatus. As shown in FIG. 4, the vehicle height adjusting apparatus includes: a movable spring receiver 8 for supporting one—side end (an upper end in FIG. 4) of a suspension spring S1 that is mounted on an outer periphery of an outer tube T of a damper D and biases the damper D in an expansion direction; and a driving mechanism M for driving the movable spring receiver 8 in an axial direction of the damper D.
The driving mechanism M includes: an annular housing 90 fixed to a side opposite to the suspension spring (an upper side in FIG. 4) of the movable spring receiver 8 on the outer periphery of the outer tube T; a jack chamber J formed between the housing 90 and the outer tube T and filled with an operating fluid; a jack piston 91 continuing to the side opposite to the suspension spring of the movable spring receiver 8 (the upper side in FIG. 4) and movably inserted between the housing 90 and the outer tube T so as to close an opening on the suspension spring side of the jack chamber J (a lower side in FIG. 4); and a pump P configured to suction and discharge the operating fluid with respect to the jack chamber J.
In a case where the vehicle height is lowered, by supplying the operating fluid to the jack chamber J by means of the pump P, the jack piston 91 is pushed out of the housing 90, and the damper D is projected, whereby the vehicle height can be raised. In a case where the vehicle height is raised, by discharging the operating fluid from the jack chamber J by means of the pump P, the jack piston 91 is pushed into the housing 90, and the damper D is contracted, whereby the vehicle height can be lowered.
JP11-182609A discloses a suspension spring force adjusting apparatus. As shown in FIG. 5, the suspension spring force adjusting apparatus includes a dust cover 2C that suppresses adhesion of dusts by covering a portion where the movable spring receiver 8 and the jack piston 91 are in sliding contact.